Why oh why. Sudden oil pressure drop.

Small block. I had a pickup tube that would not turn enough to fit the screen flat to the pan. The recommended choice was to use enough teflon tape to build a tight fit with it backed off. NO!!

I got a pipe die and screwed it on till it was finger tight and gave it 3/4's turn to retaper the threads a little. Screwed it back in to the oil pump and BANG, screen was level to pan and tight without any teflon tape.